Process for manufacturing a panel made of a thermoplastic composite

ABSTRACT

A method of manufacturing a panel made of a composite material using a tool having a support on which a lay-up is performed, the lay-up producing a stack of plies of fiber prepregs, followed by consolidating the stack aiming to obtain the panel using a compacting plate arranged above the stack. The method is implemented such that a first set of polyimide films partially covering each other is located in contact with the stack of plies, between the latter and the compacting plate.

TECHNICAL FIELD

The present invention relates generally to a method for manufacturing apanel made of a composite material, in particular a thermoplasticcomposite. For information, this may in fact involve composite materialswith a PEEK resin or PPS resin thermoplastic matrix and long carbonfibers, but also possibly composites with an epoxy resin thermosettingmatrix and carbon fibers.

The invention preferably relates to a method for manufacturing panelshaving a thickness between approximately 1 and 20 mm, such as thosetypically found in the aeronautic field, which constitutes a particularapplication for the present invention. Indeed, the method which is theobject of the invention can be implemented in order to obtain anaircraft fuselage panel, which usually has a fiber ratio close to 65%.To this end, implementation of the invention can indifferently lead toobtaining a substantially flat panel, or to obtaining a so-calledsingle- or double-curvature panel traditionally found in the compositionof aircraft fuselages. It is noted that in both of the aforementionedcases, the panel produced through implementation of the method accordingto the present invention can, of course, undergo later operations inorder to constitute a ready-to-assemble fuselage panel, operations whichmay, for example, include trying to bring back stiffeners via continuouswelding on the obtained panel, these stiffeners themselves being able tobe produced by stamping of flat plates also able to be obtainedaccording to the method of the invention.

PRIOR ART

The traditional methods for manufacturing a panel in a compositematerial consist overall of implementing two successive steps, namely alay-up step followed by a consolidation step, also called compactingstep.

The lay-up step consists of producing a stack of plies of resin fiberprepregs, each for example being in strip form, with the goal ofobtaining a plurality of layers or folds superimposed in the directionof the stack. The consolidation step of the stack consists of obtainingthe panel using a compacting plate arranged above the stack. Thiscompacting plate makes it possible, in fact, through the application ofpressure/vacuum pressure, to compact, in the direction of the stack, theunit formed by the layers of fiber prepregs, and simultaneously toevacuate the air and the gases present in the stack, such that the panelobtained has an acceptable void ratio, for example less thanapproximately 5%. This consolidation step of the stack also takes placeby applying heating to said stack, for example by placing it in asterilizer, in order to bring it to the temperature required to obtainthe fusion of the pre-impregnated resin on the fibers, and thereforewith the aim of obtaining a compact final element in one piece.

In the embodiments known from the prior art, the compacting plateusually comes into contact with the stack of plies of fibers during theconsolidation step, which can harm the final quality of the panelobtained. Indeed, it is first indicated that with this method, thesurface state of the compacting plate greatly risks being imprinted onthe upper surface of the panel obtained at the end of the consolidationstep, which may sometimes lead to incompatibility with the high surfacequality demands encountered in certain fields, such as aeronautics foraircraft fuselage panels.

Furthermore, the presence of this compacting plate in contact with thestack, also called caulking plate or sheet, prevents satisfactory airevacuation from this stack during the consolidation step. Thisrestriction can naturally lead to the appearance of porosities withinthe element obtained, synonymous with weakening of the overallmechanical resistance of this element.

SUBJECT OF THE INVENTION

The aim of the invention is therefore to propose a method formanufacturing a panel in a composite material resolving theaforementioned drawbacks, relative to the embodiments of the prior art.

To do this, the object of the invention is a method for manufacturing apanel in a composite material using tooling having a support on which alay-up step is carried out consisting of producing a stack of plies offiber prepregs, followed by a consolidation step of the stack aiming toobtain the panel using a compacting plate arranged above this stack.According to the invention, the method is implemented such that a firstset of polyimide films partially covering each other is located incontact with the stack of plies, between the latter and the compactingplate.

Thus, the glossy appearance of the polyimide films located in contactwith the upper surface of the stack during the consolidation stepadvantageously makes it possible to obtain an extremely satisfactorysurface state for the obtained panel, and which is completely compatiblewith the high surface quality demands encountered in certain fields,such as aeronautics for aircraft fuselage panels.

Furthermore, aside from the fact that this first set of polyimide filmsadvantageously makes it possible to prevent the imprinting of thesurface state of the compacting plate on the upper surface of the stack,this assembly also advantageously allows excellent drainage of gasesduring the consolidation step. This is explained by the possibleevacuation of the air and gases initially found inside the stack,through the overlapping zones of the polyimide films thereforeadvantageously forming an assembly not ensuring total sealing to thegases toward the top, in the direction of the stack of plies of fibers.

The air evacuation done is thus satisfactory, and makes it possible toarrive at a panel having a reduced void rate in relation to thatencountered previously, granting it particularly good overall mechanicalresistance properties.

The polyimide films used for the implementation of the invention can beproduced using any manner known by those skilled in the art, by reactionbetween an aromatic tetracarboxylic dianhydride and an aromatic diamine.The thickness of these films can for example be in the vicinity of 30μm, and more generally between about 20 and 50 μm.

For information, the following films, available on the market, can beused:

-   -   Thermalimide 50 micron FILM by the company AIRTECH;    -   Thermalimide 50 micron FILM by the company RICHMOND® (Ref:        UHT750); or    -   Thermalimide 50 micron FILM by the company KANEKA® (Ref: 200AV).

In general, due to the small thickness of these films, theoverlap/covering zones thereof only allow superficial marks fromimprinting to appear on the surface of the stack after the consolidationthereof, these marks in no way damaging the surface state, and notsignificantly weakening the overall mechanical characteristics of theobtained panel.

The polyimide films used, also called “thermalimides”, are naturallychosen to resist the high temperatures implemented during theconsolidation step of the stack, which can reach 400° C. or more. Thesenot having to be integrated into the final panel, they are thereforeprovided in order to be easily removed from the upper surface of thecompacted stack or of the compacting plate, for example by peeling. Inthe case most often encountered where the films used do not adhere tothe upper surface of the compacted stack or to the compacting plate atthe end of the consolidation step, the removal of these polyimide filmsobviously does not pose any particular concern.

Preferably, the method is implemented such that a second set ofpolyimide films partially covering each other is located in contact withthe stack of plies, between the latter and the support of the tooling.

Thus, the advantageous characteristics described above and obtained onthe upper surface of the panel constituted by the compacted stack canthen also be procured for the lower surface of this panel due to thepresence of this second set of polyimide films. Indeed, with such animplementation, the surface state of the tooling support isadvantageously no longer imprinted on the lower surface of the panel,since during the consolidation step, the lower part of the stack is incontact with the polyimide films covering a glossy appearance.

For information, it is preferable to offset the overlapping zones of thefirst and second sets of polyimide films considered along the directionof the stack of the plies of fibers, namely not to arrange theseoverlapping zones across from each other two by two in this direction,even if this of course remains possible, without going outside theframework of the invention.

Preferably, the method also comprises a step for placement on thecompacting plate of a first drainage fabric, this step being implementedsuch that the first fabric is located in contact with this compactingplate and separated from the first set of polyimide films by this sameplate, therefore implying that the two opposite surfaces of thecompacting plate are in contact with the first set of films and with thefirst drainage fabric, respectively. It also includes a step forplacement on the tooling support of a second drainage fabric, this stepbeing implemented such that the second drainage fabric is located incontact with the support of the tooling, between the latter part and thesecond set of polyimide films.

The aforementioned fabrics then make it possible to perform satisfactorydraining of the gases during the consolidation step of the stack, inconnection with the set of polyimide films partially overlapping eachother.

Still preferably, the method also comprises a step for placement of atleast one wedge limiting the edge effects likely to occur during thelater consolidation step of the stack, each wedge being arranged alongone edge of this stack. Preferably, the entirety of the perimeter of thestack is equipped with such wedges, which therefore allow savings inmaterial. The positive influence on the aforementioned edge effectsresults from the fact that these wedges make it possible to limit theflow of transverse material. Indeed, during the compacting operation,the compacting plate “presses on” the stack of plies. Under the effectof this pressure, the resin, which is very fluid at this temperature,tends to flow toward the edge of the plate. It “abuts” against theaforementioned wedges, also called caulking wedges. When the compactingplate reaches the caulking wedges, it exerts a normal stress thereonupon contact. Each wedge is thus subjected, in the plane of the folds,to the thrust of the resin, the normal effect of the compacting plateand its reaction on the marble plate, and therefore lastly to thefriction between the compacting plate, on one hand, and the marble plateon the other hand. This friction then prevents the wedges from movingunder the effect of the pressure from the resin, and therefore limitsthe creep of the latter and the thinning of the edges of the obtainedpanel.

Preferably, each wedge limiting the edge effects has a thicknessapproximately equal to that of the panel designed to be obtained fromthe stack, at the end of the consolidation step of this stack. Thisspecificity therefore also advantageously makes it possible to controlthe final thickness of the plate, which may therefore be smaller thanthat of the wedges. For information, one provides that the thickness ofthe wedges is, at all points of the periphery of the stack, slightlysmaller than that of the final panel, for example with a size in thevicinity of 0.1 to 0.5 mm.

However, it is alternatively possible to provide wedges whereof theinitial (nominal) thickness is, at any point of the periphery of thestack, slightly larger than that of the final panel, for example with asize in the vicinity of 0.1 to 0.5 mm. In such a case, one then makesthese wedges deformable by compression during consolidation in order,naturally, to be able to obtain the panel with the desired thickness. Asan illustrative example, the wedges can thus be produced in ahigh-temperature elastomer, such as 691PX silicone. With such aconfiguration, the edge effects are then completely eliminated.

In other words, one makes each wedge limiting edge effects have aninitial thickness larger than that of the panel designed to be obtainedfrom the stack, at the end of the consolidation step of this stack, eachwedge then being designed and arranged so as to be deformed bycompression by the compacting plate, during the implementation of thisconsolidation step.

Furthermore, it is possible to act such that each wedge limiting edgeeffects has at least one surface provided with a plurality of draingrooves, still with the aim of obtaining better draining of gases duringthe consolidation step of the stack. For information, these grooves arepreferably formed on the two surfaces opposite the caulking wedges,namely the surface in contact with the compacting plate and the surfacein contact with the marble plate serving as support. Their relativepositioning is preferably in staggered rows of one surface relative tothe other.

Furthermore, the consolidation step of the stack can be done on one handby applying a vacuum pressure within a sealed chamber partially definedby the support and in which the stack of plies and the compacting plateare located, and on the other hand by heating this same stack of pliesof fiber prepregs. However, pressure may alternatively be implemented tocompact the stack of plies of fibers without going outside the frameworkof the invention, even though this solution appears less relevant thanthat described above.

In the preferential case of the application of a vacuum pressure, oneprovides that the tooling also includes means for applying negativepressure for the sealing chamber, connected with through orificesprovided within this support, for example assuming the form of a platemade of marble, ceramic, titanium or any other suitable material knownby those skilled in the art.

With regard to the heating of the stack needed to obtain fusion of theprepreg resin during the consolidation step, one provides that thetooling also includes heating means integrated to the support. Still forinformation, these heating means can assume the form of electricalresistances and/or channels for circulation of a coolant fluid, whichare produced within the aforementioned support during manufacturing ofthe latter.

Alternatively, the tooling could be placed in a sterilizer in order tobring the stack to the desired temperature, without going outside theframework of the invention. However, the advantage of such toolingenabling performance of both the lay-up and the consolidation of thestack, is that the latter step can be done without having to move thetool incorporating the stacked, but not yet secured to each other, plieswithin it. Indeed, such an operation for moving the tooling createsrisks of relative movements between the plies forming the stack, theserisks above all being encountered when these plies are formed by athermoplastic composite, due to the absence of natural adherence ofthese plies produced in such a material.

One can provide that the method is intended to obtain, at the end of theconsolidation step of the stack, a substantially flat panel, the latterpossibly being able to be intended to undergo later operations such asforming operations of the stamping type, these operations not, however,being part of the object of the present invention.

Alternatively, the method is intended to obtain, at the end of theconsolidation step of the stack, a panel having a single curvature or adouble curvature. For information, the single-curvature panels arecalled “developable” and have a rectilinear generatrix implying thatthey can be “unwound” on a plane. On the other hand, thedouble-curvature panels, such as the cockpit fuselage panels of anaircraft, are not “developable” and therefore do not have a rectilineargeneratrix, i.e. they cannot be “unwound” on a plane. Indeed, they havea first curvature, for example in the longitudinal direction of thepanel, as well as a second curvature different from the first, forexample in the transverse direction of this same panel.

In such a case, one provides that the lay-up step is done such thatfollowing the placement of a given ply of fiber prepregs on other pliesalready stacked, the given ply is secured to at least one of the pliesof fiber prepregs already stacked, using at least one welding spot. Thisthereby makes it possible to maintain the geometry of the stack made upfor example of plies in thermoplastic composite which are not veryadhesive to each other, and for which continuous welding of theirrespective edges connecting them to each other cannot always be done, inparticular when this involves the manufacturing of a single- ordouble-curvature panel made up from successive plies not always havingthe same dimensions, and therefore being unable to be assembled two bytwo over their entire perimeter by such continuous welding due to themismatching between certain edges of successive plies.

Furthermore, while this technique of spot welding of the plies of thestack is preferably used for to manufacture panels with curvatures, itcan also be implemented to manufacture flat panels. However, in thelatter case, the continuous welding of the edges of the successive pliesconstitutes a possible solution due to the usually identical dimensionsof the different plies of the stack, even if the spot welding techniqueremains preferable.

As previously mentioned, the method is preferably applicable to themanufacturing of an aircraft fuselage panel, substantially flat, with asingle curvature, or with a double curvature, having an area which canfor example be between 10 and 30 m². To this end, it is noted that thepanel obtained by the implementation of the method according to thepresent invention can be brought to undergo later operations in order toform a fuselage panel ready for assembly. These operations include, forexample, an operation aiming to bring back stiffeners via continuouswelding on the compacted panel, these stiffeners themselves being ableto be realized by stamping of several planes also able to be obtainedaccording to the method of the invention.

Other advantages and characteristics of the invention will appear in thedetailed, non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be done with regard to the appended drawings, inwhich:

FIGS. 1 a to 1 k are views diagramming different operations performedduring the implementation of a method for manufacturing a panel made ofa composite material, according to a first preferred embodiment of theinvention; and

FIG. 2 is a view diagramming a step performed during implementation of amethod for manufacturing a panel made of a composite material, accordingto a second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In reference first to FIGS. 1 a to 1 k, one can see different successiveoperations performed during the implementation of a method formanufacturing a panel in a composite material, according to a firstpreferred embodiment of the present invention. In this first embodiment,the panel which one wishes to obtain has a substantially flat shape, andfor example globally square or rectangular, and has a thickness between1 and 20 mm. For information, it is noted that this finds a particularapplication in the aeronautics as field as a fuselage panel for anaircraft, including a fiber ratio close to 65%, for example.

In FIG. 1 a, one can see that the tooling used for the implementation ofthis method first comprises a support which can be likened to a marbleplate referenced 1. This plate 1 is passed through perpendicularly,relative to the plane along which it extends, by a plurality of throughorifices 2 provided within this marble plate 1. As will be detailed moreexplicitly below, the through orifices 2 are connected to negativepressure means 4, using a traditional fluid communication network (notreferenced) and able to assume any form known by those skilled in theart.

Furthermore, the marble plate 1 is equipped with heating means hereassuming the form of a plurality of mechanical resistances or coolantfluid circulation channels 6, which are provided integrally inside thismarble plate 1 serving as support.

The method according to the first preferred embodiment is initiated byplacing a drainage fabric 8 on the plate 1, this fabric subsequentlybeing called second tissue 8. It is, for example, formed in a mannerknown by those skilled in the art by glass fabric, such as fine glassfabric (Ref: 2165 Z6040) or coarse glass fabric (ref: 7628 TF 970) fromthe company HEXCEL Fabrics®. This second drainage fabric 8, diagrammedin FIG. 1 b, makes it possible to ensure air evacuation from the stackof plies in composite material designed to rest above this second fabric8, during the later consolidation step of this stack aiming to compactthe latter, as will emerge more clearly below.

Then, one places a set of polyimide films partially covering each other,this set referenced 10 in FIG. 1 c subsequently being called second setof polyimide films. Thus, this second set 10 is formed by a plurality ofpolyimide films 12, here three, which partially cover each other, andmore particularly two by two over so-called covering or overlappingzones. Preferably, one provides that each of the films 12 is present inthe form of a strip, and that these strips are arranged parallel to eachother as clearly shown in FIG. 1 d, even if it is alternatively possibleto consider that these strips are slanted relative to the longitudinaland transverse directions of the panel designed to be obtained. Thus,the covering zones 14 can also be likened to strips with a smaller widthoriented according to the same arrangement direction as the films 12.One preferably provides that the set 10 never has more than two films 12superimposed on each other at a given point. As shown diagrammaticallyby the arrows 16 in FIG. 1 c, it is noted that the covering zones 14 areadvantageous in that they allow the passage of air and gas during thelater consolidation step of the stack, given that at these same zones14, the sealing of the set 10 is advantageously not completely ensured.For information, the widths “l” of the covering zones 14 and the widths“l′” of the strips of polyimide films 12 vary according to the curvatureof the panel. Thus, one preferably provides for using strips with awidth “l′” of approximately 254 mm (10 inches) to manufacture flatpanels having a total area smaller than 2 m², whereas in the case wherethe total area of the flat panel is greater than 2 m², one preferablyprovides for using strips with a width “l′” of approximately 350 mm(13.8 inches).

Furthermore, in the case of a panel with curvature(s), the width “l′” ofthe component strips is in the vicinity of 350 mm (13.8 inches) forsmall curvatures, and in the vicinity of 254 mm (10 inches) forpronounced curvatures.

Furthermore, regardless of the geometry of the panel, the width “l” ofthe covering zones 14 is preferably fixed in the vicinity of 15 mm.

The polyimide films 12 used, also called thermalimides, are of coursechosen to resist high temperatures which can reach 400° C. or more, suchas those encountered during the consolidation step of the stack aimingin particular to ensure the fusion of the resin of the plies pre-soakedwith composite material. The thickness of these films 12 is preferablybetween approximately 20 and 50 μm, and the arrangement as well as thenumber of these same second films 12 are determined such that they canprevent contact between the stack of plies deposited later and themarble plate 1.

The manufacturing method is continued by performing a lay-up stepconsisting of making a stack 18 of a plurality of plies of fiberprepregs 20, along a stack direction 21 substantially orthogonal to theplane (not referenced) in which the marble plate 1 extends. Thus, theplies 20, preferably produced in thermoplastic composites, for examplewith PEEK resin or PPS resin thermoplastic matrix and long carbonfibers, are therefore arranged above each other in this stack direction21. Naturally, the number of these plies 20 each forming a layer of thestack is determined according to the desired final thickness of thepanel.

In FIG. 1 e, one can see that the lower surface of this stack 18,considered in the direction 21, is entirely in contact with the secondset of polyimide films 10. This makes it possible to ensure, for thestack later compacted, a lower surface having a surface state of verygood quality, perfectly compatible with the requirements of theaeronautical field. For information, it is noted that as the plies offiber prepregs 20 are arranged above each other, the last ply depositedcan be secured to the assembly already stacked, preferably using one orseveral weld spots for example located at the ends of each of theseplies, these usually having a substantially square or rectangular shape.This makes it possible to avoid relative movements between the differentplies 20 within the stack, which are indeed likely to take place due tothe weak mutual adherence attached to these plies in thermoplasticcomposite. It is specified that continuous welding is also possible inorder to ensure maintenance of this type without going beyond theframework of the invention.

In reference now to FIG. 1 f, one can see that the method continues byarranging wedges 22 limiting edge effects likely to occur during thelater consolidation step of the stack 18. These wedges are preferablyprovided all around the stack 18 as shown in FIG. 1 g, and thereforeeach go alongside the length of an edge of this stack. These wedges 22,which could alternatively be placed on the support 1 prior toperformance of the lay-up step, are maintained fixed on the latter plate1 using suitable assembly means, such as an adhesive tape resisting hightemperatures. The aforementioned assembly is done such that these wedges22 can still be located above the second drainage fabric 8 and thesecond set of polyimide films 10, while being in contact with thelatter.

The thickness of these wedges, corresponding to their dimension in thedirection 21, is approximately equal to that of the panel designed to beobtained from this stack 18. This specificity clearly makes it possibleto control the consolidation operation aiming to compact the stack 18,given that the thickness of this panel therefore cannot be smaller thanthat of the wedges 22 mounted on the plate 1. For information, thiswedge thickness is provided to be approximately smaller by a size of 0.1mm to 0.5 mm than that of the final panel designed to be obtained.

Furthermore, in order to ensure satisfactory drainage of the gas incombination with the second drainage fabric 8 and the first drainagefabric which will be described later, each of the wedges 22 has drainagegrooves or ridges 24 formed on their upper surface and/or lower surface,as shown diagrammatically by FIG. 1 g.

Furthermore, these wedges can each be blocked in the directiontransverse to them, and more precisely in the direction going away fromthe stack, for example using stops provided on the support 1. However,it is also possible to provide for cases where these wedges are entirelyfree in translation on the support 1, without going outside theframework of the invention.

Moreover, it is alternatively possible to provide for wedges whereof thethickness is slightly larger than that of the final panel, for examplewith a size in the vicinity of 0.1 to 0.5 mm. In such a case, thesewedges completely eliminating the edge effects are provided to bedeformable by compression during the consolidation step, in order to beable to obtain the panel with the desired thickness.

Then, one again places a set of polyimide films 26, called first set ofpolyimide films, and made up of a plurality of films 30 partiallycovering each other. This second set 26 is identical or similar to thefirst set 10 described above, insofar as it is, for example, made up ofthree (or more) polyimide films 28 partially covering each other, andmore particularly two by two on so-called covering or overlapping zones.Preferably, one provides that each of the films 28 is in the form of astrip, and that these strips are arranged parallel to each other, asclearly shown in FIG. 1 i. Thus, the covering zones 30 can also belikened to strips with a smaller width oriented in the same arrangementdirection as the films 28. One preferably provides that the set 26 neverhas more than two films 28 superimposed on each other at a given point.As shown diagrammatically by the arrows 32 in FIG. 1 h, it is noted thatthe recovery zones 30 are advantageous in the sense that they allow thepassage of air and gases during the later consolidation step of thestack, like the recovery zones 14 of the first set 10.

Still for information, the widths “l” of the covering zones 30 and thewidths “l′” of the strips of polyimide films 28 are as described above,and preferably identical to those adopted for the second set ofpolyimide films. Furthermore, the polyimide films 28 used are of thesame type as those of the first set, namely chosen to resist hightemperatures able to reach 400° C. or more, such as those encounteredduring the consolidation step of the stack aiming in particular toensure the fusion of the resin of the plies pre-soaked in compositematerial. Here again, the thickness of the films 28 is preferablybetween approximately 20 and 50 μm, and the arrangement as well as thenumber of these same first films 28 are determined such that they canprevent contact between the stack of plies 20 deposited, and thecompacting plate placed later. To do this, as shown diagrammatically inFIG. 1 i, the first set 26 is provided to extend over the entire uppersurface of the stack 18, but also to overhang on each of the wedges 22,which can possibly also be completely covered by the first films 28. Asshown in FIG. 1 i, in the longitudinal direction of the strips 28, thesepreferably slightly exceed the wedges 22, which is not the case for theother wedges arranged transversely. To this end, one could even providethat the strips 28 do not cover these same wedges 22 arrangedtransversely, without going beyond the framework of the invention.

Insofar as the upper surface of this stack 18, considered in thedirection 21, is entirely in contact with the first set of polyimidefilms 26, this also makes it possible to ensure, for the stack latercompacted, an upper surface having a very high-quality surface state,perfectly compatible with the requirements of the aeronautic field.

As is best visible in FIG. 1 h, the covering/overlapping zones 30 of thefirst set 26 are each located across from one of thecovering/overlapping zones 14 of the second set 10, in the direction 21.Nevertheless, it would also be possible to offset these overlappingzones 14, 30, namely to arrange them other than by placing them acrossfrom each other two by two in this same direction 21. However, it isadvisable for these overlapping zones 14, 30 preferably to remain all incontact with the lower surface or the outer surface of the stack not yetcompacted, i.e. in contact with the first or last ply 20 deposited.

As shown in FIG. 1 j, and prior to the consolidation step of the stack18, a step is done to place a compacting plate 36, also called caulkingplate or sheet, produced in a traditional metal material such as astainless steel. This plate 36 is arranged above the stack 18, such thatits lower compacting surface is in contact with the first set 26 ofpolyimide film 28. As shown diagrammatically by FIG. 1 j, its dimensionsare provided in order to possibly be able to abut against each of thewedges 22 provided all around the stack 18. Naturally, the compactingplate 36 is arranged substantially parallel to the plate forming thesupport 1, given that the desired panel must have a substantially flatshape.

The manufacturing method is continued by placing a first drainage fabric34 above the compacting plate 36, as also shown in FIG. 1 j. Of course,it is noted that this first drainage fabric 34 has a role identical tothat played by the second drainage fabric 8 previously described, theonly difference between these two fabrics 8, 34 being that they aredesigned to be connected to a lower surface of the stack 18 and to anupper surface of said stack, respectively. For this reason, it cantherefore be a fabric of the same type, having the same drainageproperties.

The last operation performed before implementation of the consolidationstep of the stack 18 consists of creating a sealing chamber 40 using themarble plate 1, on which one mounts a sealing bladder 42 covering all ofthe aforementioned elements, as visible in FIG. 1 k. To do this, thebladder 42 is stuck all around the stack 18 on the marble plate 1 usingone or several set screws 45 screwed into the latter part, the screwhead 45 squeezing a sealing device 44 resting in contact with this sameplate 1. For information and as shown in the figure, the two drainagefabrics 8 and 34 can also be stuck on the sealing device 44 via the setscrew 45, by placing them between the bladder 42 and this same sealingdevice 44.

Thus, the plate 1 and the sealing bladder 42 together form a sealingchamber 40 within which the stack of plies of fiber prepregs 20 isfound, which can then undergo said consolidation operation aimingglobally to compact this stack 18.

To do this, one simultaneously implements the heating means 6, as wellas the negative pressure means 4 making it possible to create a vacuuminside the chamber 40 using through orifices 2 located within the plate1, and opening in this same chamber 40. More precisely, the heatingmeans are actuated so as to apply a temperature in the vicinity of 400°C. within the stack 18, so as to cause the fusion of the resin necessaryfor compacting of this stack. Naturally, as previously mentioned, thepolyimide films 20 and 28 are designed to bear such temperatures, suchthat they are not damaged during the consolidation step. When the vacuumis produced inside the chamber 40 through the orifices 2, the bladder 42then applies pressure on the compacting plate 36 which thus tends tocome closer to the support plate 1 by moving orthogonally to thedirection of the stack 21. Thus, by moving in this way under the actionof the bladder 42, the plate 36 in contact with the first set ofpolyimide films 26 creates sticking of the plies 20 in the stackdirection 21 against the plate 1, these plies then tending to compactand become integral with each other thanks to the fusion of the prepregresins on these same plies. This consolidation step is done until thepanel obtained by compacting has a thickness in the direction 21 whichis the desired thickness, and is at any rate capped by the thickness ofthe wedges 22, when this is provided to be slightly smaller than thefinal thickness of the panel. When this target thickness is reached, atthe end of the consolidation step, the chamber 40 is opened bywithdrawing the bladder 42, and the compacted stack obtained forming thedesired panel can then be removed from the tooling.

For information, the chamber 40 is opened by removing the bladder 42 andthe compacted stack obtained forming the desired panel can then beremoved from the tooling. It may potentially be necessary to remove thepolyamide films 12, 28 which continue to adhere to the upper and/orlower surfaces of the obtained panel. However, it is noted that thepolyimide/thermalimide films are usually such that at the end of theconsolidation step of the stack 18, they do not adhere to any of theother elements provided to perform this step, such that their removaladvantageously does not constitute any particular problem.

Now in reference to FIG. 2, one can see a second preferred embodimentaccording to the present invention, the aim of which is no longer toobtain a substantially flat panel, but a panel with a single or doublecurvature.

For information, this type of panel is traditionally found in theaeronautic field, as a fuselage panel of an aircraft.

FIG. 2 illustrates the state of the tooling and the stack of plies asthey exist just before the consolidation step of this same stack iscarried out. It therefore corresponds to the state shown in FIG. 1 k inthe case of the first preferred embodiment of the invention.

As one can see in this FIG. 2, all of the operations having led to thisassembly are similar to those described for the first embodiment inreference to FIGS. 1 a to 1 k. It is noted that this assemblynevertheless differs from that encountered in the first embodiment bythe shape of certain elements of the tooling used, as well as by theabsence of wedges limiting the edge effects which were not provided for.Nevertheless, these could be arranged in the same way as described forthe first embodiment without going beyond the framework of theinvention.

Thus, in order to obtain the single or double curvature for the fuselagepanel, the marble support 1 no longer assumes the form of a flat plate,but has a geometry which is complementary to that desired for one of thetwo surfaces of the panel. Similarly, the compacting plate 36 has acompacting surface which is no longer flat, but which has a geometrywith a shape complementary to that of the other of the two surfacesneeding to be produced for the panel. Of course, although FIG. 2 shows aconcave support surface and a convex compacting surface of the plate 36,an inverted configuration between these convex and concave surfaces(each with single or double curvatures) could naturally be consideredwithout going beyond the framework of the invention.

Another difference with the first preferred embodiment lies in thesecuring between the different layers 20 in thermoplastic composite ofthe stack 18, which have a weak adherence. Indeed, given that the singleor double curvatures sought for the panel leads to the superposition ofstrips having different widths, the mismatch between the edges of thesestrips therefore sometimes prevents securing of two directly consecutivestrips by continuous welding all around them. To face this problem, wethen consider, instead of welding these plies all around theirperimeter, welding them by one or several carefully chosen weld spots.This manner of proceeding can be adopted for securing each of the pliesof fibers 20 beginning from the second one in the stack, given that thefirst naturally cannot be secured on the support 1 in this way. Thus, inorder to ensure correct maintenance of the first ply of the stack 18relative to this same marble support 1, sticking of this first ply 20against the surface of the support of the plate 1 can be re-implemented,via negative pressure application done using the means 4. Indeed, whenaspiration is done using these same means 4, even before the bladder 42has been placed on the support 1, the air sucked in through the throughorifices 2 advantageously causes sticking of the first ply 20 of thestack 18 against this same marble support 1. This thereby makes itpossible to use the negative pressure application means 4 for a purposeother than the main purpose aiming to later provide the vacuum withinthe sealing chamber 40, in order to perform the consolidation step ofthe stack 18.

Another particularity of this second preferred embodiment of the presentinvention consists of obtaining the precise shape of the compactingplate 36, constituting part of the tooling. Indeed, this plate 36 isadvantageously made in a material including mica and resin, as describedin patent application BE 758 263, or also found under the commercialbrand MIGLASIL® offered by the company VON ROLL ISOLA®, which grants itproperties enabling it to be deformable during the first heating up, andto become extremely stiff once this first heating up is completed. As aresult, this plate 36 is produced in the aforementioned material, andcoarsely preformed to approach the final geometry required. During itsfirst use for the production of a panel with single or doublecurvatures, this preformed plate is arranged in the manner previouslydescribed, namely on the first set of polyimide films 26. Then, duringthe consolidation step of the stack of plies of fibers at hightemperature, the compacting plate 36 will on one hand deform, stickingagainst this stack 18, and will simultaneously reach its firingtemperature from which this plate 36 becomes stiff. As a result, it isonly once this plate has been totally formed to the stack 18 under theeffect of the pressure applied by the sealing bladder 42 that this willadopt its precise final form, which can then be kept during all laterheating up, due to the specific properties of the material used.

Thus, this plate 36 with very precise curvature can then be used toproduce subsequent panels using this same tooling, since it will beperfectly capable of preserving, during the following compacting stepsat high temperatures, its precise shape adopted during the first firing.

Without going beyond the framework of the invention, it wouldalternatively be possible to provide a plate manufactured so as to haveits precise definitive shape directly, without it therefore beingnecessary to resort to the manufacturing of a first panel to obtain thisshape.

Of course, various changes may be made by one skilled in the art to theinvention which has just been described, solely as non-limitingexamples.

1-16. (canceled)
 17. A method for manufacturing a panel in a compositematerial using a tooling having a support on which a lay-up isperformed, the lay-up producing a stack of plies of fiber prepregs,followed by consolidation of the stack aiming to obtain the panel usinga compacting plate arranged above the stack, implemented such that afirst set of polyimide films partially covering each other is located incontact with the stack of plies, between the stack and the compactingplate.
 18. The manufacturing method according to claim 17, implementedsuch that a second set of polyimide films partially covering each otheris located in contact with the stack of plies, between the stack and thesupport of the tooling.
 19. The manufacturing method according to claim18, further comprising: placement on the compacting plate of a firstdrainage fabric, implemented such that the first fabric is located incontact with the compacting plate and separated from the first set ofpolyimide films by the same plate; and placement on the support of thetooling of a second drainage fabric, implemented such that the seconddrainage fabric is located in contact with the support of the tooling,between the latter part and the second set of polyimide films.
 20. Themanufacturing method according to claim 17, further comprising placementof at least one wedge limiting edge effects likely to occur during thelater consolidation of the stack, each wedge being arranged along anedge of the stack.
 21. The manufacturing method according to claim 20,wherein each wedge limiting the edge effects has a thicknessapproximately equal to that of the panel designed to be obtained fromthe stack, at the end of the consolidation of the stack.
 22. Themanufacturing method according to claim 20, wherein each wedge limitingthe edge effects has at least one surface including a plurality ofdrainage grooves.
 23. The manufacturing method according to claim 20,wherein each wedge limiting the edge effects has an initial thicknessgreater than that of the panel designed to be obtained from the stack,at the end of the consolidation of the stack, each wedge being designedand arranged so as to be deformed by compression by the compactingplate, during implementation of the consolidation.
 24. The manufacturingmethod according to claim 17, wherein the consolidation of the stack isperformed by applying negative pressure within a sealing chamberpartially defined by the support and in which the stack of plies and thecompacting plate are located, and by performing heating of the samestack of plies of fiber prepregs.
 25. The manufacturing method accordingto claim 24, wherein the tooling also includes a negative pressureapplication mechanism for the sealing chamber, connected to throughorifices provided within the support.
 26. The manufacturing methodaccording to claim 25, wherein the support assumes a form of a marbleplate.
 27. The manufacturing method according to claim 24, wherein thetooling also comprises a heating mechanism of the stack of plies offiber prepregs, the heating mechanism being integrated to the support.28. The manufacturing method according to claim 17, to obtain, at theend of the consolidation of the stack, a substantially flat panel. 29.The manufacturing method according to claim 17, to obtain, at the end ofthe consolidation of the stack, a panel having a single curvature. 30.The manufacturing method according to claim 17, to obtain, at the end ofthe consolidation of the stack, a panel having a double curvature. 31.The manufacturing method according to claim 29, wherein the lay-up isperformed such that following placement of a given ply of fiber prepregson other already-stacked plies, the given ply is secured to at least oneof the plies of already-stacked fiber prepregs, using at least one weldpoint.
 32. The manufacturing method according to claim 17, applied tomanufacture of an aircraft fuselage panel.